Brush carriage for selector switches



June-9,1942. c. N, HlcKMAN 2,285,657

BRUSH CARRIAGE RoR SELECTOR swITcHEs Filed Dec. 2e, 1940 FIG? A TTORNEV Patented June 9, 1942 BRUSH CARRIAGE FOR SELECTOR SWITCHES Clarence N. Hickman, Jackson Heights, N. Y., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York ` Application December 26, 1940, Serial No. 371,672

(Cl. 20o-171) 6 Claims.

This invention relates to selector switches for establishing connections in machine switching telephone systems and, more particularly, to a brush carriage for a selector switch of the type having access to banks of terminals.

Panel type selector switch frames are provided with one or more flat or panel banks of terminals with which the brush sets of a plurality of selector switches cooperate. In some types of selector switches such, for example, as that disclosed in Patent 2,173,548, granted September 19, 1939, to W. W. Carpenter and R.. F. Mallina, the brush carriage is driven at a very high speed to traverse the brushes carried thereby along rows of terminals of panel banks. Some difficulty has heretofore been experienced in securing reliable contacts between such brushes andr the bank terminals due to the vibratory movement imparted to the brush carriage or to the bank by building vibrations or duev to the movement of other switches mounted on the same frame and cooperating with the same bank of terminals. This difficulty has been largely overcome by the provision of a brush carriage of the type disclosed in Patent 2,164,034, granted to me on June 27, 1939 in which the four brush springs are attached to a sled which rests on the ends of the terminals of the rows of bank terminals with which the switch is assigned to cooperate and which is provided with parallelly disposed portions or ribs which enter between the edges of adjacent rows of terminals whereby the sled is guided in its movementl over the rows of terminals. The sled is arranged for movement longitudinally over the rows of terminals and since it is pressed against the banks by a roller, spring supported on the sled, which engages a member secured between the end brackets of the switch unit and positioned parallel to the face of the bank, the entire brush carriage may partake of any lateral vibratory movement of the face of the bank and, as a consequence reduce the tendency of the brushes to slide with respect to the bank terminals upon which they have been arrested in the selective movement of the switch.

It is an object of the present invention to further reduce the objectionable noise imposed on the speech transmission circuit in which switch brushes of the above described type are included, by providing that the tip and ring brushes of the brush carriage shall not engage bank terminals during the terminal selection movement of the switch and that all of the brushes oi the brush carriage shall, due to their improved construction, make better contacts with bank terminals.

It is a further object of the invention to so improve the construction of the brush carriage and the construction of the brushes thereof that the amount of power required to traverse the brush carriage in its terminal selection movement is materially reduced.

In accordance with the invention these objects are attained by securing the four brush springs to the brush carriage with the contact shoes ci the two inner springs engaging the edges of the two inner rows of terminals of the bank with which the switch is assigned to cooperate, for example, with the test and metering terminals, and with the contact ends oi the two outer springs positioned for engagement with the edges of the two outer rows of terminals, that is, the tip and ring terminals but held out of engagement with such terminals until the brush carriage has been arrested with the contact shoe of its test brush spring engaged with the test terminal of a desired terminal set. Since the tip and ring brush springs have no sliding movement over the edges of the terminals of the rows with which they cooperate, they require no contact shoes and may be of the vrelay spring type thereby insuring better contact engagement with the bank terminals. For engaging such springs with the bank terminals, the brush carriage is provided with a small magnet, the armature of which are positioned to press the contact ends of such springs against the edges of the tip and ring bank terminals of the set opposite which they have been positioned by the selective movement of the brush carriage.

The two inner brush springs are, in accordance with the present invention, of the so-called wafer type. That is their contact shoes, due to the improved construction, are much thinner than Contact shoes heretofore provided and therefore provide greater clearance from the inner edges of the tip and ring rows of bank terminals with a better insurance against snagging thereon during the movement of the brush carriage. The Contact portion of the end of each of these springs is raised from the body of the spring and is flanked on each side by a slider insulated from the spring, the contact portions and the sliders having chromium-plated surfaces to reduce friction. By this construction, a metal-to-metal contact between the brush spring shoe and the edges of the terminals is always insured thereby eliminating the fouling of terminals and chemical reactions thereat by the engagement of insulating portions of brush spring shoes therewith as was possible with the contact shoes of the type heretofore employed. Actual tests have shown a very marked improvement with the metal-to-metal engagement.

For a more complete understanding of the invention, reference may be had to the following detailed description taken in connection with the accompanying drawing in which:

Fig. 1 is a side elevational view of a brush carriage constructed in accordance with the invention;

Fig. 2 is a top plan view of the brush carriage disclosed in Fig. 1;

Fig. 3 is a rear elevational View of the brush carriage of Fig. 1;

Fig. 4 discloses in perspective the portions of a partially assembled brush spring; and

Fig. 5 is a perspective view of the brush spring of Fig. 4 completely assembled.

The brush carriage comprises two parallelly disposed frame members I and Z, preferably of a light non-magnetic material. such as aluminum, between the lower ends of which is positioned a grooved spacing block 3 also of aluminum. Positioned in the grooves of the block 3 are two strips 4 and 5 of insulating material which serve as guide ribs to guide the brush carriage along a row of terminal sets of a terminal bank. The ends of these strips are rounded oft as indicated at 6 to prevent snagging on the edges of terminals. The spacing between the inner surfaces of these strips is made only slightly greater than the combined width of the two inner rows of bank terminals and the strips are sufciently thin to permit them to move freely between the inner and the outer rows of terminals of the row of terminal sets to which the brush carriage is assigned. Positioned outside of the frame members I and 2 are two shoes 'I and 8 of insulating material, the outer surfaces 9 and Iii of which are so positioned as to ride on the ends of the outer rows of terminals of the terminal sets and which have rounded corners as indicated at II to prevent them from snagging on terminals. The shoes 'I and 8, the spacer 3 and the guide strips 4 and 5 positioned within the grooves of the spacer 3, are secured together and to the ends of the frame members I and 2 by the rivets I2.

Positioned between the upper ends of the frame members I and 2 is a spacer I 3 of aluminum, flanked by two strips I4 and I5 of insulating material provided at their upper ends with portions I 6 and I'I which serve as guide ribs to guide the upper end of the brush carriage along a row of bank terminal sets. These guide ribs have their inner surfaces spaced by the spacing block I3 so that such spacing is only slightly greater than the combined width of the two inner rows of bank terminals as disclosed more clearly in Fig. 2I and have the ends of such surfaces rounded off as indicated at I8 to prevent snagging on the edges of the terminals during the movement of the brush carriage. Positioned between the guide members or ribs I6 and II is a shoe I9 of insulating material for sliding engagement against the ends of the two inner rows of bank terminal sets. This shoe is retained in position against the edge of the spacer I3 by ears 2i) formed in the edges thereof which are engaged in notches in the top and bottom edges of the guide ribs I6 and I'I. To prevent the shoe from rounded off as indicated at 2I.

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of the strips I4 and I5 and of the spacer I3 are clamped by bolt 24 between the ears 22 bent parallelly from the edges of the bracket 23.

The lower end of the bracket 23 is secured to the spacer I3 by a screw 25 which extends through a hole in the bracket into a threaded hole in the spacer I3. The upper ends of the bracket is bent outwardly at right angles and is provided with a rectangularly shaped hole through which the threaded flat shank of an adjusting screw 26 extends and which shank is retained therein by the nut 21 threaded thereon. The screw 26 is provided with an eyelet to which one end of the brush carriage driving tape of the switch may be secured. By the provision of the flat shank on the screw and a rectangular hole in the bracket through which the shank extends, the rotation of the screw is prevented when the nut 21 is turned on the thread of the screw to adjust the tension of the driving tape.

Assembled outside of the two strips I4 and I5 and positioned adjacent to their outer surfaces are two brush springs 28 and 29, to be later described, and interposed between each of these springs and the inner surfaces of the frame members I and 2 are spacing blocks 30 preferably of aluminum insulated from the springs by strips 3I of insulating material. Assembled outside of the frame members I and 2 are two additional brush springs 32 and 33, to be later described, which are insulated from the frame members I and 2 by interposed strips 34 of insulating material. The strips I4 and I5, insulating strips 3| and 34, spacers I3 and 3l), springs 28, 29, 32 and 33 are secured to the upper ends of the frame members I and 2 by screws 35 which extend through aligned holes in the clamping plate 36 and insulating strip 31, through aligned holes in the aforesaid insulating strips, brush springs, spacers, and frame members, thence through aligned holes in the insulating strip 38 into tapped holes in the clamping plate 39; These screws are suitably insulated from the brush spring by sleeves of insulating material which surround the Shanks of such screws.

Extending between the frame members I and 2 at a position substantially mid-way of their length is a magnet core 40, the ends of which are reduced in diameter and extend through holes in .the frame members I and 2. A magnet coil 4I surrounds the core 40 and has two spoolheads 42 of insulating material to each of which is attached a coil terminal lug 43.

The frame lmembers I and 2 are provided with extensions 44, the ends of which are notched to receive a flat -bar 45 of magnetic material, the bar being held in place by staking the ends of the extensions 44 as indicated at 46 in Fig. 1. An armature 41 is pivoted to each end of the bar 45 by headed pins 48 whose shanks extend freely through holes in the hinge ends of the armatures and have drive ts into holes in the ends of the bar 45. The free ends of the armatures are provided with studs 48 of insulating material which are engaged by the outer brush springs 32 and 33. The core 40, bar 45 and armatures 4I constitute a complete magnetic circuit whereby when the coil 4I is energized, the armatures are attracted toward the ends of the core 4|) and press the brush springs 32 and 33 inwardly against the outer edges of the tip and ring terminals of the two outer rows of terminals of a selected terminal set. To serve as backstops for the armatures 4'I, the tongues 5U are struck from the frame members I and 2 and bent outwardly and upwardly astbestfdisclosedinFigJ 3 against'which thearmaturesrare normally engaged bythe pretensionedbrush springsi32 and 33.

A channel-shapedbracket 5 I isclampedaround the outside Aof the'lower shoes 9 'and I0 .by a bolt 53 which extends Vthrough aligned holes in the flanges 52 of such bracket, through holes in the shoes 9 and l0, in the frame members I and 2 and in the spacedblock 3. Oneiiange of this bracket is bent outwardly and hasriveted thereto the arm 54. The upper edge of the arm'54 is bent 'at right angles as indicated at155 to add rigidity thereto and is provided with a cylindrical sleeve portion 56 in which the end of acable of flexible conductors may be secured. The arm 54 is also provided with tabs 51 and 59 struckl up therefrom for holding in .place the conductors extending from the flexible cable of conductors to Vthe soldering lugs, 'such as 59, of the brush springs 28, 29, 32and'33. The web of the bracket 5I is extended as a tabBI) Yto which the other end of the driving tape may be secured.

Each of the brush springs is substantially L- shaped, as disclosed most clearly in Fig. 5, and comprises an upper rectangular supporting section 6I having an elongated opening '62 vtherein through which theclamping screws 35'and their insulating sleeves may extend, a rearwardly extending soldering lug 59 and a downwardly extending spring arm 63. The arms of the outer or tip and ring brushes 32 and 33 are'bifurcated at their free ends like relay springs and each section thus formed has welded thereto a contact bar 64 as illustrated in Figs. 2 and 3. Brush springs 3?. and 33 are similar except `that the spring 32 is slightly longer than the spring 33 and thatthe contact bars 64 are positioned on one face of spring 32 and on the opposite Tface of spring 33.

Springs V28 and 29 are each provided with a contact shoe of the type disclosed in Figs. 4 and 5. To form the shoe the spring is bent transversely near its free end and slotted to form two raised or contact portions 65 and 66 and its edges are notched at either end of the raised portions as indicated at 61 in Fig. 4. Each notch has its central portion more deeply cut as indicated at 68 for a purpose to be later described. Positioned transversely across the spring on each side of the raised contact portions 65 and 66 is a strip 69 of insulating fiber, rendered iiexible during the assembly operations by soaking, having the rectangular holes 10 therein. The ends of the strip are bent downwardly and seated in the oppositely disposed notches 61 as best illustrated in the partly assembled brush spring of Fig. 4 and are then bent upwardly against the back surface of the brush spring. Positioned on each strip 69 is a slider plate 1I, of the shape disclosed in the upper portion of Fig. 4, preferably stamped :from phosphor bronze sheet material. In assembling a slider on the spring, it is positioned on the ber strip 69 with its tongue portion 12 positioned in the slot between the raised portions 65 and 66 but out of contact therewith and with its clamping arms 13 aligned with the notches formed in the ends of the strip 69 by the holes 19 thereof when such strip is bent over the edges of the spring as previously described. Arms 13 are then bent downwardly into such notches but out of contact with the edges of the spring due to the deepened portions 68 of the notches 61 and are then bent upwardly against the ends of the strip 69 on the back of the spring whereby the slider is clamped to the spring and insulated "therefrom by .the 'insulating strip. .The completely'assembled .brush springappears as disclos'ed in Fig. 5. The exposed faces ofthe sliders 1I and portions65 vand 66 are preferably polished and then chromium .plated vto reduce wear and to reduce friction. The brush springs 28 and 29 are similar except that the :spring 28 is slightly longer than the spring 2'9 andthe sliders and raised portions are positioned on one face of spring 28 and on the oppositeface of `spring 29.

YIt will be noted that with this spring construction, the contact shoe is very thin thus insuring that the back of the spring will not engage the terminals of an adjacent row ofthe terminal bank during the movement of the brush carriage. Furthermore, during the movement of the brush vshoe along a row of bank terminals, a metal-tometal contact is always made without danger of cross-connecting adjacent or succeeding terminals of the row and, since the surfaces of the tongue portions 12of'the sliders, where theyproject into the slots between'the raised portions 65 and 66, are only Vslightly below the contact faces of such raised portions, there is no tendency for the raised portions to snag on terminals `and no vtendency to produce a bouncing of the end of the brush spring when the contact portions ride over the edge of v a terminal. Since there vis no insulating material brought into engagement with the edge of the terminal bythe movement of the brush shoe thereover, the fouling of'the Contact surfaces of bank terminals 'by the deposit of insulating material thereon is obviated.

For maintaining the brush `carriage shoes in engagement against the ends of the terminals of the rows of bank terminals with which they are assigned to cooperate, a U-shaped spring 14 is provided, one arm of which is looselysecured to the bracket 5I by rivets `15 and the other arm of whichterminates in two ears '16 and 11 between which a roller 18 is rotatably secured by the pivot rivet 19. The roller engages the inner face of the channel member 80, the ends of which are secured to plates (not shown) secured to the end brackets of the switch in such a manner as to position the face of the channel member parallel to the face of the terminal bank. The roller end of spring 14 is so positioned that with the roller engaged on the face of the channel member 80, the shoes 8, 9 and I9 of the brush carriage are firmly forced against the ends of the bank terminals. The channel member also serves as a guide for the depending loop of the flexible cable (not shown) one end of which is secured in the sleeve 56 of the brush carriage arm 54, The channel member 8| serves the same purpose in connection with the brush carriage of a second switch of the same switch unit. To prevent the brush carriage from falling back from the face of the bank `when it is abruptly stopped in its movement, a bumper stud 82 is secured to the bar 45 with its end normally slightly spaced from the face of the channel member 80.

When the brush carriage is moved in either direction by the tape attached to the eyelet of screw 26 and to the tab 66, the shoes 8, 9 and I9 are held firmly against the ends of the rows of bank terminals by the engagement of roller 18 with the inner face of channel member 8U and are guided along the rows of terminals by the guide ribs 4, 5, I6 and I1. The contact shoes of the brush springs 28 and 29 engage successive terminals of the two inner rows of terminals, that is, the sleeve or test and the meter control terminals, but the outer brushes 32 and 33 do not engage terminals of the two outer or tip and gring rows of terminals. When, however, the test or sleeve brush, for example brush 28, engages a marked sleeve terminal, the circuit of coil 4I may becompleted in any desired manner whereby the armatures 41 become attracted to move the contact Vends of the springs 32 and 33 into engagement with the tip and ring terminals of the terminal set in which such test terminal is located.

" What is claimed is:

1. In a brush for a selector switch, a exible spring member having a raised contact portion extending transversely thereof adjacent to its free end, and a slider insulatedly supported on said spring on each side of said raised contact portion.

2. In a brush for a selector switch, a flexible spring member having a raised portion extending transversely thereof adjacent to its free end and divided into two contact sections by a slot extending axially of the spring, `and a slider insulatedly supported on said spring on eachv side of said raised portion and each having a tongue portion extending into the slot between said contact sections.

3. In a brush for a selector switch, a flexible spring member having a raised portion extending transversely thereof adjacent to its free end and divided into two contact sections by a slot extending axially of the spring, and a slider in- -sulatedlysupported on said spring on each side of said raised portion and each having a tongue portion extending into the slot between said contact sections, said contact portions and said sliders having their exposed surfaces polished and chromium plated to reduce wear and friction.

4. In a brush for a selector switch, a flexible spring member having a raised portion extending transversely thereof adjacent to its free end and divided into two contact sections by a slot extending axially of the spring, a band of insulating material surrounding said spring on either side of said raised portion and a slider supported on each of said bands adjacent to said raised portion having tabs bent over on the back surface of said band for clamping it in position and each having a tongue portion extending into the slot between said contact sections.

5. In a brush for a selector switch, a flexible spring member having a raised portion extending transversely thereof adjacent to its free end and divided into two contact sections by a slot extending axially of the spring and having oppositely disposed notches in its edges at each side of said raised portion, a band of insulating material seated in each pair of said notches and surrounding said spring, and a slider supported on each of said bands adjacent to said raised portion'having tabs bent over on the backsurface of said band for clamping it in position, `and each having a tongue portion extending into the slot between said contact sections.

6. In a brush for a selector switch, a flexible spring member having a raised portion extending transversely thereof adjacent to its free end and divided into two contact sections by a slot extending axially of the spring and having oppositely disposed notches in its edges at each side of said raised portion, a band of insulating material seated in each pair of said notches and surrounding said spring and having notches in the portions thereof which are bent over the edges of said notches and a slider supported on each of said bands adjacent to said raised portion having tabs bent over on the back surface of said band and lying in the notches thereof and each having a tongue portion extending into the slot between said contact sections.

CLARENCE N. HICKMAN, 

